Resumo O objetivo deste trabalho foi calcular os valores de erosividade e realizar o mapeamento da erosividade mensal e anual das chuvas na Bacia do Rio Manuel Alves da Natividade, região sudeste do estado do Tocantins, com base no interpolador Krigagem ordinária (KO), a partir da avaliação de desempenho dos modelos esférico, exponencial e gaussiano, a partir de dados de precipitação referente ao período de 1983 a 2013. A geoestatística foi aplicada para o mapeamento da erosividade tanto na escala mensal quanto na anual. A erosividade anual apresentou valores entre 8.332 e 9.253 MJ mm ha-1 h-1 ano-1, com auge em dezembro, quando atingiu valores de até 2.170 MJ mm ha-1 h-1 ano-1 por mês. De maio a setembro, a erosividade apresentou valores inferiores ao crítico, tido como 500 MJ mm ha-1 h-1 ano-1 por mês. Foram identificadas três regiões críticas para ações de planejamento visando a conservação do solo e da água: noroeste, norte e central da bacia do rio Manuel Alves da Natividade.

Abstract The objective of this work is to calculate the values of erosivity and map the monthly and annual rainfall erosivity in the Manuel Alves da Natividade river basin in the southeastern region of the state of Tocantins, Brazil, based on ordinary kriging (KO) interpolator and the performance evaluation of the spherical, exponential and Gaussian models using rainfall data for the period 1983-2013. Geostatistics was applied to map erosivity on both monthly and annual scales. The annual erosivity showed values between 8,332 and 9,253 MJ mm ha-1 h-1 year-1, with a peak in December, when it reached values of up to 2,170 MJ mm ha-1 h-1 year-1 per month. From May to September, erosivity presented values lower than critical, considered as 500 MJ mm ha-1 h-1 year-1 per month. Three critical regions were identified for planning actions aiming soil and water conservation: the northwest, the north and the central area of the Manuel Alves da Natividade river basin.

Abstract Background: Proteases play an important role for the proper physiological functions of the most diverse organisms. When unregulated, they are associated with several pathologies. Therefore, proteases have become potential therapeutic targets regarding the search for inhibitors. Snake venoms are complex mixtures of molecules that can feature a variety of functions, including peptidase inhibition. Considering this, the present study reports the purification and characterization of a Kunitz-type peptide present in the Dendroaspis polylepis venom as a simultaneous inhibitor of elastase-1 and cathepsin L. Methods: The low molecular weight pool from D. polylepis venom was fractionated in reverse phase HPLC and all peaks were tested in fluorimetric assays. The selected fraction that presented inhibitory activity over both proteases was submitted to mass spectrometry analysis, and the obtained sequence was determined as a Kunitz-type serine protease inhibitor homolog dendrotoxin I. The molecular docking of the Kunitz peptide on the elastase was carried out in the program Z-DOCK, and the program RosettaDock was used to add hydrogens to the models, which were re-ranked using ZRANK program. Results: The fraction containing the Kunitz molecule presented similar inhibition of both elastase-1 and cathepsin L. This Kunitz-type peptide was characterized as an uncompetitive inhibitor for elastase-1, presenting an inhibition constant (Ki) of 8 μM. The docking analysis led us to synthesize two peptides: PEP1, which was substrate for both elastase-1 and cathepsin L, and PEP2, a 30-mer cyclic peptide, which showed to be a cathepsin L competitive inhibitor, with a Ki of 1.96 µM, and an elastase-1 substrate. Conclusion: This work describes a Kunitz-type peptide toxin presenting inhibitory potential over serine and cysteine proteases, and this could contribute to further understand the envenomation process by D. polylepis. In addition, the PEP2 inhibits the cathepsin L activity with a low inhibition constant.

Abstract Background: Bitis arietans is a venomous snake found in sub-Saharan Africa and in parts of Morocco and Saudi Arabia. The envenomation is characterized by local and systemic reactions including pain, blistering, edema and tissue damage, besides hemostatic and cardiovascular disturbances, which can cause death or permanent disabilities in its victims. However, the action mechanisms that provoke these effects remain poorly understood, especially the activities of purified venom components. Therefore, in order to elucidate the molecular mechanisms that make the Bitis arietans venom so potent and harmful to human beings, this study reports the isolation and biochemical characterization of a snake venom serine protease (SVSP). Methods: Solubilized venom was fractionated by molecular exclusion chromatography and the proteolytic activity was determined using fluorescent substrates. The peaks that showed serine protease activity were determined by blocking the proteolytic activity with site-directed inhibitors. In sequence, the fraction of interest was submitted to another cycle of molecular exclusion chromatography. The purified serine protease was identified by mass spectrometry and characterized biochemically and immunochemically. Results: A serine protease of 33 kDa with fibrinogen-degrading and kinin-releasing activities was isolated, described, and designated herein as Kn-Ba. The experimental Butantan Institute antivenom produced against Bitis arietans venom inhibited the Kn-Ba activity. Conclusions: The in vitro activities of Kn-Ba can be correlated with the capacity of the venom to provoke bleeding and clotting disorders as well as hypotension, which are common symptoms presented by envenomed victims. Obtaining satisfactory Kn-Ba inhibition through the experimental antivenom is important, given the WHO's recommendation of immunotherapy in cases of human accidents with venomous snakes.